Solar isn't being used for critical loads, but it is still helping

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eBay has installed a 100 KW solar array on its data center in Denver. That's not enough power to run a data center, but Tom Price, eBay's Global Data Center Services manager, said the system, which was completed last November, is delivering benefits.

The solar array is taking up approximately 18,000 square feet of the 21,000-square-foot data center roof. In an interview, Price outlined the project.

How is the power being used? The power runs non-critical loads, meaning it is being used to supply office space power. This includes equipment such as the desktops used by the data center's 35 employees. The office power is segregated from the data center loads.

How much power is produced by the solar array ? The system produces more power than needed. The excess power is sent to the electrical grid, and eBay gets credit from the local power company for that power. The system can produce up to 500 kWh a month in the peak summer months. About half of that is needed to power the office. The solar system doesn't have storage and consequently only supplies power when the sun is out.

Does the solar system work with snow cover? With two inches of snow cover, the solar array will still produce power, thanks to improvements in the technology. In January, the system produced 196 kWh, its low, which is typically one of the snowier months of the year. That ability to still produce power with snow cover was a big benefit when eBay looked into this system.

What was the payback period? With government incentives, tax rebates and rebates from the energy provider, eBay is estimating a 3.5 year return on investment.

What was on the data center 's roof prior to installation? The data center building was originally built for offices and had a heat absorbing ballasted roof with 350,000 pounds of rock on it. The rock was removed and replaced with a rubber membrane coating which was painted bright white to reflect the sunlight.

What did the rock removal mean for your data center? Once the rock was removed, heat was no longer being trapped in the data center. The data center saw a 1.5% decrease in the overall need in air conditioning units, a significant decrease. eBay is running this data center at 76 degrees Fahrenheit.

What prompted eBay to put the solar panels in? The company has a willingness to explore new or renewable energy options. The goal is to offset some of the carbon used by the data centers. The company has installed a 625 KW solar array on its Silicon Valley campus. It is exploring other options at additional facilities, including wind power.

Are there any maintenance issues associated with the solar panels? None yet. The panels have already been through several hail storms this season with no damage and have proven to be very reliable.

What is the life expectancy of these panels? eBay is expecting 25 years out of these panels, which is what they are warrantied for.

How does office equipment handle the transition from solar to electric grid? There is no interruption, it's all transparent.

Has this experience influenced you or members of your staff to investigate solar panels for home use? It has. Price said he and others at eBay are investigating solar panels for their homes .

Patrick Thibodeau covers SaaS and enterprise applications, outsourcing, government IT policies, data centers and IT workforce issues for Computerworld. Follow Patrick on Twitter at @DCgov or subscribe to Patrick's RSS feed . His e-mail address is [email protected] .